Disubstituted N-cyanodithioiminocarbonates have utility as intermediates in organic synthesis. For example, dimethyl N-cyanodithioiminocarbonate is an intermediate in the preparation of H2-antihistamines, such as cimetidine. Dimethyl N-cyanodithioiminocarbonate is also used in the manufacture of antiulcer and antisecretory compounds and is an intermediate in the preparation of many heterocycles.
Hantzsch and Wolvekamp, Liebigs Ann. Chem. 331:265 (1904) and Timmons and Wittenbrook, J. Org. Chem. 32:1566 (1967) describe the preparation of dimethyl N-cyanodithioiminocarbonate by the methylation of dipotassium N-cyanodithioiminocarbonate. The process of Timmons and Wittenbrook involves the methylation of the dipotassium N-cyanodithioiminocarbonate in aqueous acetone with one equivalent of methyl iodide. The potassium methyl N-cyanodithioiminocarbonate product is then isolated in about 95% yield. Then, the potassium methyl N-cyanodithioiminocarbonate is treated with another equivalent of methyl iodide in acetone which produces dimethyl N-cyanodithioiminocarbonate in about 58% yield.
Wittenbrook, J. Heterocyclic Chem. 12:37 (1975) describes the preparation of dimethyl N-cyanodithioiminocarbonate from the dipotassium salt of N-cyanodithioiminocarbonic acid by a simultaneous addition of two molar equivalents of methyl iodide to an acetone suspension of the dipotassium salt of N-cyanodithioiminocarbonic acid. Hungarian Patent No. 181,743 (Reiter) describes a reaction with an aqueous ethanol solution of the dipotassium salt of N-cyanodithioiminocarbonic acid. Wieland, Ph.D. dissertation, West Virginia University (1971) describes a reaction with an ethanol suspension of the dipotassium salt of N-cyanodithioiminocarbonic acid. Suyama and Odo, J. Syn. Org. Chem., Japan, 29:65 (1971) describe the addition of two molar equivalents of base to a suspension of carbon disulfide (CS.sub.2), cyanamide (H.sub.2 NCN) and methyl iodide (CH.sub.3 I).
Walek, Preiss, and Dietzel, Z. Chem. 18(4):144 (1978) describe the preparation of dimethyl N-cyanodithioiminocarbonate by adding one equivalent of dimethyl sulfate to a mono-methyl N-cyanodithioiminocarbonate dissolved in acetone. Trompen, Geevers, and Hackmann, Rec. Trav. Chim. 90:463 (1971) describe a methylation of the dipotassium salt of N-cyanodithioiminocarbonic acid in water. Hungarian Patent No. 181743 (Reiter) describes a reaction with the addition of two molar equivalents of dimethyl sulfate or a methyl halide in a solvent of aqueous ethanol, aqueous 1-propanol or aqueous 2-propanol. Czechoslovakian Patent No. 221221 (Vejdelek et al.) describes the addition of two molar equivalents of a methyl halide or dimethyl sulfate in a solvent of aqueous ethanol, aqueous 1-propanol or aqueous 2-propanol.
For the purposes of the invention the term "symmetrical" characterizes a disubstituted N-cyanodithioiminocarbonate as having two identical substituent groups R. For the purposes of the invention the term "unsymmetrical" characterizes a disubstituted N-cyanodithioiminocarbonate as having two different substituent groups R. For example, a compound of the general formula I ##STR5## may be a symmetrical or unsymmetrical compound because each R may be independently defined, for example, as any suitable substituent group. A compound of the following formula I-A ##STR6## is a symmetrical disubstituted N-cyanodithioiminocarbonate because both of the substituent groups are methyl. A compound of the following formula I-B ##STR7## is an unsymmetrical disubstituted N-cyanodithioiminocarbonate because one substituent group is methyl and the other substituent group is ethyl.
For the purposes of the invention, the term "metal salts" includes metal salts having monovalent, bivalent and fractions of polyvalent metals sufficient to balance the anionic charge in the salt. Mixed metal salts are also contemplated. Also, the term "metal hydroxide" includes hydroxides of monovalent, bivalent and fractions of polyvalent metals.
For the purposes of the invention, the term "Group 1 or Group 2 metals" includes all metals from Groups 1 and 2 of the Periodic Table.
Also, for the purposes of the invention, the term "methanolic solvent system" includes methanol, aqueous methanol, or any mixture of solvents including methanol. For example, a methanolic solvent system may include methanol and one or more other solvents, such as water, ethanol or acetone.